package com.wc.AlgoOJ_homework.AlgoOJ_HomeWork2.G_GCD;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.StringTokenizer;

/**
 * @Author congge
 * @Date 2024/3/5 22:30
 * @description http://43.138.190.70:8888/p/530?tid=65e6b15c27489dab814f8d41
 */
public class Main {
    static FastReader sc = new FastReader();
    static PrintWriter out = new PrintWriter(System.out);
    static long a, b;

    public static void main(String[] args) {
        a = sc.nextInt();
        b = sc.nextInt();
        // 这个c=b-a一定是最大的gcd(a+k,b+k)=gcd(a+k,b-a)
        long c = b - a;
        // 是的a+k并且多一个c,a/c表示在a前面有几个c，那么后面得最多再多加一个c就好了
        // 如果c>=a,那就说明是a到达第一个c几号
        if (c < a) c = (a / c + 1) * c;
        long k = c - a;
        out.println(k);
        out.flush();
    }
}

class FastReader {
    StringTokenizer st;
    BufferedReader br;

    FastReader() {
        br = new BufferedReader(new InputStreamReader(System.in));
    }

    String next() {
        while (st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }

    int nextInt() {
        return Integer.parseInt(next());
    }

    String nextLine() {
        String s = "";
        try {
            s = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return s;
    }

    long nextLong() {
        return Long.parseLong(next());
    }

    double nextDouble() {
        return Double.parseDouble(next());
    }

    // 是否由下一个
    boolean hasNext() {
        while (st == null || !st.hasMoreTokens()) {
            try {
                String line = br.readLine();
                if (line == null)
                    return false;
                st = new StringTokenizer(line);
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return true;
    }
}
